He never flirts with me or comes on to me sexually. He says he loves me but how?

Well, relationships are very complex, it's in the core of our existence but the definition of love and relationship change as you ask different people. Love is complex, that's something we need to take into account, and people love and show love in different ways, meaby that person loves you for your being, for the person you are and is attracted to you out of the sexual aspects, but as always, I think communication is the key in any relationship, perhaps if you talk with him about what's going on and hear what's his point on things, it will help you understand your partner and your relationship as a whole and perhaps also find a solution.